EM

If we want to find the maximal point of $x$$x$ for the function $f(x)$$f(x)$, we can introduce another parameter $y$$y$ to help

take $f(x)$$f(x)$ apart into

where $y^k$$y^k$ is easy to find, $\underset{y}{\text{min}}\mathrm{\Delta }(x^k,y)=0$$\mathop{\text{min}}\limits_{y} \Delta(x^k, y)= 0$

step 1 [M]

fix $y\equiv y^k$$y \equiv y^k$

step 2 [E]

fix $x=x^{k+1}$$x = x^{k+1}$

In all

So

Comment:

By introducing another parameter $y$$y$, and iterate step 1 [M] and step 2 [E], we eventually find the maximal point of $x$$x$ for the function $f(x)$$f(x)$